This paper studied the value of lateral transshipment policy between two competitive retailers under demand disruption environment． Considered two retailers competing for selling homogeneous products，we assumed that retailers can use inventory pooling strategy to mitigate customer demand risks when demands are disrupted．Thus，three non-cooperative game models are established: no disruption and no transshipment case (NDNT) ，with disruption and no transshipment case ( WDNT) ，and with disruption and with transshipment case ( WDWT) ．Through a contraction mapping theory，we developed sufficient conditions for the Nash equilibrium to be existent and unique．We proved that each game of the three cases has a single pure strategy Nash equilibrium at symmetric configuration．Furthermore，we analyzed properties of the equilibrium and compared it with the other one．We also analyzed the monotone relationships of the competition degree parameters to the equilibriums based on solutions of partial derivatives equations and developed sufficient conditions that the transshipment policy is beneficial to the retailers． Through computation and simulation of a numerical example，we verified these conclusions．It is shown that retailers are always benefited from lateral transshipment when demands are disrupted because expected revenue will realize Pareto improvement after transshipment．However，relatively low transshipment prices will make retailers hurt by transshipment．Therefore，transshipment price configuration plays a key role in managing demand disruptions with transshipment．The results will provide theoretical supports for entities regarding disruption management．